In industrial or manufacturing settings, such as for petroleum refining, data, measurement values, control signals, and the like are generally transferred between control systems and one or more field devices (e.g., sensors or actuators), requiring a large number of interface circuits. The connection or input/output (IO) pins for conventional interface circuits communicating with the industrial environment are typically designated in general, based on the function for the IO pins. Generally, the function of an IO pin is determined by the physical properties of the signal, upstream or downstream higher system functions, and the system configuration. The field devices present interfaces that generally fall into one of four input/output (IO) function categories, Analog Input (AI), Digital Input (DI), Analog Output (AO), or Digital Output (DO).
In a hazardous environment, the interface circuits to the field devices are required to be intrinsically safe devices. An intrinsically safe device is defined as being incapable of releasing electrical or thermal energy to cause ignition of a volatile gas or gaseous mixture. Typically, an intrinsically safe environment has a safe side and a hazardous side. The device located on the hazardous side must meet the intrinsically safe requirements. The associated devices located on the safe side and electronically linked to the device located on the hazardous side must also be intrinsically safe.
In an intrinsically safe application, it is a common practice to use an intrinsically safe barrier as a safety buffer between a device located on the hazardous side and an apparatus located on the safe side. For example, when a thermocouple is placed in a hazardous area to measure a temperature, the thermocouple is connected to an associated temperature reading apparatus via an intrinsically safe barrier. Both the associated temperature reading apparatus and the intrinsically safe barrier are placed in the safe area. The thermocouple, in this usage, and other devices that are used on the hazardous side of an intrinsically safe environment are commonly referred to as field devices.
The limitations of existing intrinsic safety device implementations are numerous. The current IO devices that are software configurable do not support intrinsically safe applications. External intrinsic safety devices have to be added to software configurable IO devices in order to allow these devices to be used in a hazardous application. Unfortunately, these external intrinsic safety devices take up additional space, require a separate enclosure and dedicated custom wiring in order to be connected to the desired field device.